At his home in the foothills town of Waynesville, N.C., a former Marine staff sergeant named Jimmy Massey says he still struggles with the nightmares, even awake.

Mostly, he says, he dreams about incoming mortar shells, always startled out of his slumber before they land. During the day, a simple tire screech can severely shake him. He sees garbage bags on the roadside and imagines explosive devices inside of them.

Massey was in Iraq during the war’s first weeks in 2003. He was honorably discharged that year and diagnosed with post-traumatic stress disorder.

Once home, he began telling horrific tales: Of Marines committing atrocities in Iraq, deliberately — almost gleefully — gunning down unarmed Iraqis, including small children. He repeated his claims, sometimes differing in their details, in widely distributed media reports.

Then last month, a St. Louis newspaper reporter who was embedded with the battalion labeled the allegations as exaggerated or plainly false.

The result has been an uproar. Massey — a 12-year Marine veteran and a former Marine recruiter — has been hailed as a hero by a handful of anti-war activists, and vilified on conservative Web sites as a liar whose falsehoods were readily regurgitated by the mainstream media.

What remains unclear — and perhaps may never become clear, lost in the fog of war and the passage of time — is exactly how much of what he said actually happened, and how much amounts to nothing more than the nightmares of one Marine.

Massey, now 34, was attached to the 3rd Battalion, 7th Marines Weapons Company, known as the 3/7.

Among his most vivid claims, and apparently among the most dubious, is his account of his unit firing on a group of unarmed Iraqi demonstrators on April 8, 2003, near the Rashid military complex outside Baghdad.

“The demonstrators were my first kill,” he wrote in “Kill! Kill! Kill!” a memoir unpublished in the United States. “I got one for sure and I felt (expletive) incredible afterwards. Man, what an adrenaline rush! The feeling of fear becomes your power. It drives you.”

In a May 2004 interview with a freelance writer for The Sacramento Bee, Massey described “trigger-happy” Marines who “lit up” the demonstration after hearing a stray gunshot.

“You fired into six or 10 kids?” he was asked. “Were they all taken out?”

“Oh, yeah,” Massey answered.

In his book, Massey describes shooting one demonstrator square in the chest and says the rest of the encounter unfolded this way:

“I quickly acquired a new target, another Iraqi demonstrator kneeling on the ground trying to find a quick exit. I quickly aimed at his head, took a deep breath, exhaled and fired another shot at this head. One head: boom! Another head: boom! One center mass: boom! Another center mass: boom! I continued to do this until I perceived no movement in the demonstrators’ bodies.”

In a lengthy telephone interview with The Associated Press, Massey repeated his claim that his unit — and he personally — fired on the demonstrators. He said four were killed. He said his original estimate of 10 was inaccurate.

But reporters and a photographer who were embedded with the 3/7 say there is no evidence such a shooting happened — indeed, no evidence that the Marines confronted any demonstrators so early in the war.

“There was certainly no organized protesting, no ‘Go home,’ anything like that,” said Ravi Nessman, an AP reporter who knew Massey while he was embedded with Weapons Company. “When (the Marines) were driving into central Baghdad, they were cheered.

“Things went bad much later.”

Ron Harris, the St. Louis Post-Dispatch reporter whose November article called into question Massey’s claims, said neither he nor any Marine he has interviewed remembers a protest.

“What demonstrators?” he asked in a phone interview. “It was almost like a parade atmosphere. People had been lining the streets for blocks to see these Marines drive by.”

A Marine spokesman at the Pentagon, Maj. Douglas Powell, said an internal probe found Massey’s claims regarding “the killing of innocent civilians” to be untrue.

“It was investigated and found to be unsubstantiated in regard to law-of-war violations or violations of the rules of engagement,” he said.

Powell declined to discuss the investigation in detail. Massey told the AP he was never interviewed by the Marines in the probe.

A Marine spokesman at Twentynine Palms, where Massey’s unit was based, declined to make any Marines who were part of the battalion available for interviews. He said he was acting at the direction of the Pentagon.

And nearly a dozen Marines who served with Massey and are now out of the military, contacted by AP, either did not return phone calls for comment or declined to speak about Massey. Some said they did not want to give him additional publicity.

Powell said he arranged for Harris, who was embedded with the 3/7, to speak to Marines who served alongside Massey or who were in the Rashid military complex that day, and Harris reported none recalled seeing any demonstrators.

Lt. Kevin Shea, who was commander of Massey’s platoon, told the Post-Dispatch about 20 Iraqis did approach the Marines to ask what was happening.

Shea told the newspaper he explained what the Marines were doing, and the Iraqis returned to their homes.

Massey has suggested Harris set out to smear him, but Harris insists there was nothing personal in his reporting. He says he set out to see whether he could prove — not disprove — Massey’s allegations.

“I wrote stories that did not paint a pretty picture” of the early days of the war, Harris says.

“I’m damn sure not covering for the Marine Corps.”

According to Massey, later on the same day as the purported demonstration, Marines fired on a white Toyota that came toward a military checkpoint. Moments later, he claims several Marines fired on and killed the driver, who had gotten out and was standing with his hands up.

He told the AP it was then that he began seriously questioning what was happening. He said he had heard reports of other Marine units killing women and children, and confronted his commanding officers.

“They had already labeled me kind of a rogue,” he said. “I was very cautious and leery about what was taking place, especially with the killing of innocent civilians.”

On the following day, April 9 — the day Baghdad fell and Iraqis pulled down an iconic statue of Saddam Hussein — Massey claims his unit fired on a red Kia Spectra that failed to stop at a checkpoint.

He claims three occupants of the car were killed, their bodies later dumped unceremoniously on the side of the road. The one remaining survivor, he says, confronted him and cried in anguish: “You killed my brother!”

The Marines say they have found no evidence either of the episodes happened.

Nessman, the embedded AP reporter, says he spoke to Massey and another Marine as they rested in the front of their Humvee at the Baghdad stadium where the battalion was based on April 10 or 11, and says they were discussing having shot a single civilian in a car who failed to stop at a checkpoint.

But Nessman stresses he never saw any Marine intentionally kill an unarmed civilian, and he adds: “None of the story that Jimmy tells later did he tell me that day.”

Both the Marines and the embedded reporters readily acknowledge that innocent civilians were killed, particularly during the chaotic days around the fall of Baghdad.

Rules of engagement allowed the Marines “to engage what they felt was an imminent threat coming at them,” Powell says. “It didn’t just happen once with this unit, it happened multiple times. It’s an unfortunate part of conflict.”

Massey, the reporters and the Marines seem to agree on this much: The confusion in the war’s early days was enormous, if not blinding.

In early April 2003, some Marines would stand on major streets holding up the palms of their hands, attempting to order vehicles to stop. Iraqis may have been confused by the unfamiliar signal.

“The Marines were still on a war footing,” Nessman says. “They had been told there were cars rigged with bombs. They were told to shoot on anyone who got close to them. Any car that got near them, they were shot.”

“There were a lot of civilians shot, no question,” he says.

But Massey, both in public appearances and in his book (which has been published only in France), has gone much further than suggesting innocent civilians were accidental casualties.

In a speech at Cornell University in March 2005, Massey asked of the Marines, “How is a 6-year-old child with a bullet in his head a terrorist, because that is the youngest I killed,” according to a newspaper account.

Massey told the AP the remark about the 6-year-old was simply a rhetorical question he asked of his commanders in Iraq.

He maintains today that some of the killings of civilians were deliberate, and that some Marines appeared to enjoy it.

“Whenever you’re in combat, you see a side of human nature that’s very dark,” he says. “I felt that at some levels of what we were doing, some of the levels of brutality were borderline psychopathic behavior.”

Still, important discrepancies have emerged in Massey’s accounts over the past two years.

For example, at a Dec. 8, 2004, hearing in Toronto for an Army deserter seeking asylum in Canada, Massey claimed his unit killed 30 civilians in a 48-hour period in April 2003.

But Massey said in the AP interview that only those three incidents, with a total of eight killings, happened over April 8 and 9, and that the figure of 30 civilian deaths represents a three-month period.

In the wake of Harris’ November Post-Dispatch article — headlined, “Is Jimmy Massey telling the truth about Iraq? Witnesses, including us, say the answer is no” — attention focused on other reports in the media that had quoted Massey.

The Associated Press quoted Massey five times between May 2004 and October 2005 — four times directly, and once citing a CBC report in which Massey said his unit had committed “cold-blooded, calculated murder.”

In each case, Massey alleged his platoon had killed innocent civilians or committed atrocities against Iraqis. Two of the five stories included Marine Corps denials of Massey’s allegations.

“Clearly our stories should have included the firsthand observations of our own embedded reporter,” said AP Managing Editor Mike Silverman.

When Massey gave a speech at a local college in March, the Albany, N.Y., Times Union reported some of his claims but did not include a response from the Marine Corps. In November, Editor Rex Smith told readers the paper “didn’t deliver the full truth.”

The Sacramento Bee, which published Massey’s account of alleged atrocities in its Forum section a year and a half ago, admitted to readers that Nov. 13 it had made an error of judgment in failing to look further into Massey’s charges or calling the Marines for a response.

“It was clear in retrospect that we hadn’t done due diligence with the Jimmy Massey interview,” said David Holwerk, The Bee’s editorial page editor.

In a note to readers, he added: “I’d like to be able to tell you who’s telling the truth in all this, but I can’t. Is it Jimmy Massey, a decorated Marine veteran with an honorable discharge? Or is it Ron Harris, an experienced reporter who lived alongside Marines in Iraq?”